Doesn't the theory of infinite collisions existing, require that you are nit restricting the file size? The combination of "the hashes match" and the file sizes are roughly the same would seem to go beyond a reasonable doubt.
Not really. Let's use for example a 256 bit hash and a 1KB file. That means you have about 2 ^ (1024 * 8 - 256) collisions that are the exact right size. Close enough to infinite for any file that's at least a hundred bytes. The more pressing concern is how hard it is to fake a particular hash.
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Doesn't the theory of infinite collisions existing, require that you are nit restricting the file size? The combination of "the hashes match" and the file sizes are roughly the same would seem to go beyond a reasonable doubt.
Not really. Let's use for example a 256 bit hash and a 1KB file. That means you have about 2 ^ (1024 * 8 - 256) collisions that are the exact right size. Close enough to infinite for any file that's at least a hundred bytes. The more pressing concern is how hard it is to fake a particular hash.
However, Igor's statement does hold true for (some) hashes that are at least as long as the maximum file size :P
Thanks for explaining. +1.